Collapsible Panels with Toolbar and in Forms

[nrueckmann]

Like often with Nova I'm not sure if this is a bug or feature request. Anyhow the feature of collapsing panels introduced in 4.2.6 seems to be unfinished. I can not see any technical reason why collapsing is disabled for panels with a toolbar or within the form view.
So my proposal is: Allow us to have collapsible panels with a toolbar and allow us to use them on forms.